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Watermelon powdery mildew fungicides for 2008
By Amanda Gevens, Assistant Professor, UF/IFAS Plant Pathology Department
Quintec is a new fungicide which provides excellent control of powdery mildew on cucurbits. At this time, Quintec is labeled for only watermelon and cantaloupe. Quintec cannot be applied more than four times per season and no more than two times consecutively. It should be rotated with another effective fungicide with a different mode of action. There are two choices: 1) a strobilurin ( Flint , Quadris or Pristine) or 2) a DMI, or demethylation inhibitor, (Nova/Rally or Procure). All of these rotation partners have been losing efficacy over the past several years. there have been recent reports of resistance to Pristine in Georgia. Given this information, Nova/Rally or Procure may be preferred.
Products that provide limited or no control of powdery mildew on watermelon (or other cucurbits) include: fixed copper, mancozeb, maneb, zoxamide+mancozeb (Gavel), and mefenoxam (Ridomil).
Growers should scout cucurbits for powdery mildew early, and begin applications immediately if symptoms are present. Look for white powdery spots on leaves, petioles, and stems that are in shaded areas of the plant canopy. If you find powdery mildew in your field, begin treatments immediately and reapply on a 7-day interval.
Most effective fungicides |
Rate |
Comments |
Myclobutanil (Nova/Rally)
|
2.5-5.0 oz/A |
Resistance risk, combine with a protectant to extend usefulness; 30 day plant back restriction |
Quinoxyfen (Quintec)
|
6 fl oz/A |
Do not make more than 4 apps.; do not make more than 2 consecutive apps. |
Triflumizol (Procure)
|
4-8 oz/A |
Begin app. at vining or first sign of disease, repeat every 7-14 days |
Effective fungicides |
|
|
Sulfur
Trifloxystrobin ( Flint )
Azoxystrobin (Quadris)
Kresoxim methyl (Sovran)
Pyraclostrobin (Cabrio)
Pyraclostrobin + boscalid (Pristine) Thiophanate methyl (Topsin)
Horticultural oils |
See label
1.5-2.0 oz/A
11-15.4 fl oz/A
3.2-4.8 oz/A
12-16 oz/A
12.5-18.5 oz/A
|
Do not use in warm weather, may cause phytotoxicity
Limit 4 apps. per season; alternate chemistry
Limit 4 apps. per season; alternate chemistry
Limit 4 apps. per season; alternate chemistry
Limit 4 apps. per season; alternate chemistry
|
